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What’s in all that space between the stars? Space gloop!

The vast emptiness of space isn't really so empty: It's filled with space goop made of greasy carbon molecules.

You'll need windshield wiper if you want to drive to Mars. (Tesla/Big Think)

To say that space is “full of” anything must inevitably be an overstatement. The distances between objects in space are so vast that it’s mostly emptiness, at least as far as we can detect—dark matter, we’re looking at you. Nonetheless, it’s not the barren nowhereland punctuated occasionally by the odd meteorite we see in sci-fi, either. There’s lots of hydrogen out there, and there’s lots of carbon, too. And those two things come together to form greasy molecules, or “aliphatic hydrocarbon.” A new study has calculated for the first time just how much of this “space grease” there is. In our own Milky Way alone, the study concludes, there’s some 10 billion trillion trillion—that’s a 1 followed by 34 zeroes—metric tons of the sticky goo. When you finally get your own personal spaceship, you’ll need windshield wipers.



Illustration of a greasy carbon molecule. Gray spheres are carbon, white ones are hydrogen. (D. Young)

Stars and planets are the products of a continuous cycle of coming together and breaking apart of materials, propelled outward by immense energy releases from stars. The so-called interstellar medium (ISM) is a slurry of unattached materials floating around and potentially available for new star or planet formation.


Interstellar medium (Shutterstock)

It’s believed that carbon is the fourth most abundant element in the ISM. Small molecules containing carbon form in stars’ cores after which they clump together to form larger carbon molecules or grains—up to 70% of space carbon is thought to be found in such grains. Released to the circumstellar regions around the stars, the carbon molecules and grains are eventually borne outward on stellar winds.

Scientists have suspected about half of the carbon out there in the ISM is pure carbon, and the rest is greasy aliphatic carbon and mothball-like aromatic carbon. (Mothballs are made of naphthalene, and aromatic carbon is a gaseous version.) But it’s not clear how much non-pure carbon there is. The mission of the new study was to figure this out.

The team of scientists from the University of New South Wales and Ege University re-created lab conditions similar to those that lead hydrogen and carbon to join in space to form the grease.


Scanning electron microscopy of lab-created grease molecule (B. Gu ̈nay, et al)

“The interstellar dust analogues produced in the laboratory enable us to better understand the nature of the dust particles in the ISM,” says the study. “In this study, we produced reliable dust analogues from gas phase precursor molecules by mimicking interstellar/circumstellar conditions.” The team calculated a 3.4μm absorption coefficient using both FTIR and 13C NMR spectroscopy. By applying the coefficient to the known carbon at the center of the Milky Way, they deduced that “The resultant aliphatic carbon column densities are least five times higher than some values reported previously.” That works out to about 54−135 parts per million of the carbon at galaxy center. As the study puts it, “This leaves a substantial proportion of the dust-bound carbon to be found in aromatic or olefinic structures.”

Though the University of South Wales’ UNSW Newsroom cheekily notes that’s about the equivalent of a trillion trillion trillion pats of butter, it’s not something you’d want to eat. “This space grease is not the kind of thing you’d want to spread on a slice of toast,” co-author Tim Schmidt tells UNSW. “It’s dirty, likely toxic and only forms in the environment of interstellar space—and our laboratory.”

Next up, the scientists will attempt to work out how much of what’s left is aromatic molecules.

We are stardust/We are golden/We are million-year-old carbon — Joni Mitchell, “Woodstock”

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Cognitive psychologist Weizhen Xie (Zane) of the NIH's National Institute of Neurological Disorders and Stroke (NINDS) works with people who have intractable epilepsy, a form of the disorder that can't be controlled with medications. During research into the brain activity of patients, he and his colleagues discovered something odd about human memory: It appears that certain basic words are consistently more memorable than other basic words.

The research is published in Nature Human Behaviour.

An odd find

Image source: Tsekhmister/Shutterstock

Xie's team was re-analyzing memory tests of 30 epilepsy patients undertaken by Kareem Zaghloul of NINDS.

"Our goal is to find and eliminate the source of these harmful and debilitating seizures," Zaghloul said. "The monitoring period also provides a rare opportunity to record the neural activity that controls other parts of our lives. With the help of these patient volunteers we have been able to uncover some of the blueprints behind our memories."

Specifically, the participants were shown word pairs, such as "hand" and "apple." To better understand how the brain might remember such pairings, after a brief interval, participants were supplied one of the two words and asked to recall the other. Of the 300 words used in the tests, five of them proved to be five times more likely to be recalled: pig, tank, doll, pond, and door.

The scientists were perplexed that these words were so much more memorable than words like "cat," "street," "stair," "couch," and "cloud."

Intrigued, the researchers looked at a second data source from a word test taken by 2,623 healthy individuals via Amazon's Mechanical Turk and found essentially the same thing.

"We saw that some things — in this case, words — may be inherently easier for our brains to recall than others," Zaghloul said. That the Mechanical Turk results were so similar may "provide the strongest evidence to date that what we discovered about how the brain controls memory in this set of patients may also be true for people outside of the study."

Why understanding memory matters

person holding missing piece from human head puzzle

Image source: Orawan Pattarawimonchai/Shutterstock

"Our memories play a fundamental role in who we are and how our brains work," Xie said. "However, one of the biggest challenges of studying memory is that people often remember the same things in different ways, making it difficult for researchers to compare people's performances on memory tests." He added that the search for some kind of unified theory of memory has been going on for over a century.

If a comprehensive understanding of the way memory works can be developed, the researchers say that "we can predict what people should remember in advance and understand how our brains do this, then we might be able to develop better ways to evaluate someone's overall brain health."

Party chat

Image source: joob_in/Shutterstock

Xie's interest in this was piqued during a conversation with Wilma Bainbridge of University of Chicago at a Christmas party a couple of years ago. Bainbridge was, at the time, wrapping up a study of 1,000 volunteers that suggested certain faces are universally more memorable than others.

Bainbridge recalls, "Our exciting finding is that there are some images of people or places that are inherently memorable for all people, even though we have each seen different things in our lives. And if image memorability is so powerful, this means we can know in advance what people are likely to remember or forget."

spinning 3D model of a brain

Temporal lobes

Image source: Anatomography/Wikimedia

At first, the scientists suspected that the memorable words and faces were simply recalled more frequently and were thus easier to recall. They envisioned them as being akin to "highly trafficked spots connected to smaller spots representing the less memorable words." They developed a modeling program based on word frequencies found in books, new articles, and Wikipedia pages. Unfortunately, the model was unable to predict or duplicate the results they saw in their clinical experiments.

Eventually, the researchers came to suspect that the memorability of certain words was linked to the frequency with which the brain used them as semantic links between other memories, making them often-visited hubs in individuals's memory networks, and therefore places the brain jumped to early and often when retrieving memories. This idea was supported by observed activity in participants' anterior temporal lobe, a language center.

In epilepsy patients, these words were so frequently recalled that subjects often shouted them out even when they were incorrect responses to word-pair inquiries.

Seek, find

Modern search engines no longer simply look for raw words when resolving an inquiry: They also look for semantic — contextual and meaning — connections so that the results they present may better anticipate what it is you're looking for. Xie suggests something similar may be happening in the brain: "You know when you type words into a search engine, and it shows you a list of highly relevant guesses? It feels like the search engine is reading your mind. Well, our results suggest that the brains of the subjects in this study did something similar when they tried to recall a paired word, and we think that this may happen when we remember many of our past experiences."

He also notes that it may one day be possible to leverage individuals' apparently wired-in knowledge of their language as a fixed point against which to assess the health of their memory and brain.

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